Siren



FIG. 1 is a top, front, right side perspective view of a siren showing our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a right-side elevation view thereof;

FIG. 5 is a left-side elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

In the drawings the broken lines depict portions of the siren that form no part of the claimed design. 

CLAIM The ornamental design for a siren, as shown and described. 